vt-pbf 
Serialize Mapbox vector tiles to binary protobufs in javascript.
Usage
As far as I know, the two places you might get a JS representation of a vector tile are geojson-vt and vector-tile-js. These both use slightly different internal representations, so serializing each looks slightly different:
From vector-tile-js
var vtpbf = require('@mapcat/vt-pbf')
var VectorTile = require('@mapcat/vector-tile').VectorTile
var data = fs.readFileSync(__dirname + '/fixtures/rectangle-1.0.0.pbf')
var tile = new VectorTile(new Pbf(data))
var orig = tile.layers['geojsonLayer'].feature(0).toGeoJSON(0, 0, 1)
var buff = vtpbf(tile)
fs.writeFileSync('my-tile.pbf', buff)From geojson-vt
var vtpbf = require('@mapcat/vt-pbf')
var geojsonVt = require('geojson-vt')
var orig = JSON.parse(fs.readFileSync(__dirname + '/fixtures/rectangle.geojson'))
var tileindex = geojsonVt(orig)
var tile = tileindex.getTile(1, 0, 0)
// pass in an object mapping layername -> tile object
var buff = vtpbf.fromGeojsonVt({ 'geojsonLayer': tile })
fs.writeFileSync('my-tile.pbf', buff)